The present invention relates to systems and methods for evaluating vehicle motion signals to improve a vehicle""s performance.
Throughout the development of an automobile, testing is required to determine whether the vehicle is performing to design specification. For example, the performance of a vehicle""s frame and suspension is tested over rough road conditions to ensure the vehicle can withstand the road conditions as well as provide a minimum level of comfort and safety for vehicle occupants.
Typically, sensors are disposed at various locations on the vehicle to measure the vehicle""s motion. The sensor signals are then processed by an in-vehicle control and processing system. More specifically, the signals are transferred from the time domain to the frequency domain using the Fast Fourier Transform (FFT) method to obtain a frequency spectrum for the given vehicle motion signals. The frequency spectrum may then be analyzed to determine whether the vehicle is vibrating at its natural frequencies. If the amplitude of the vibration at the vehicle""s natural frequencies is unacceptable for vehicle durability and occupant comfort and safety reasons, changes would then be made to the vehicle""s frame/body and/or suspension.
While conventional methods and systems for evaluating a vehicle""s performance by acquiring and analyzing vehicle motion signals using FFT to determine the frequency content of the signals achieved their intended purpose, many problems still exist. For example, current systems and methods require significant processing power and storage resources. Current methods (i.e. FFT) are impractical for use in production embedded systems, such as a production vehicle control and stability system. Thus, frequency analysis of vehicle motion signals has been limited to the testing and the development stages of a vehicle on pre-production vehicles.
Therefore, what is needed is a new and improved system and method for analyzing vehicle motion signals for subsequent use by a production vehicle embedded system, such as a production vehicle control and stability system. The new and improved system and method must be suitable for embedded systems having restricted computational resources and storage facilities.
In accordance with an aspect of the present invention, a method and system is provided for acquiring and analyzing vehicle motion signals to improve vehicle performance. The sampled vehicle motion signals are transferred from the time domain to the frequency domain using an online frequency analysis. Once the frequency spectrum for the sampled vehicle motion data is obtained, the frequencies of interest and associated amplitudes are identified. Depending on the type of test conducted and the vehicle components to be analyzed, the natural frequencies of interest will be known and identified in the frequency spectrum. For example, during a rough road test the natural frequencies of interest in a yaw rate signal for determining the performance of the frame/body and the vehicle suspension are 2 Hz and 10 Hz respectively. The present invention provides a weight filter matrix to calculate the frequency spectrum of interest in real time. The matrix is pre-calculated in accordance with the given sampling time, sampling rate, and frequencies of interest. More specifically, for rough road analysis, the frequencies of 2 Hz, 4 Hz, 6 Hz, 8 Hz, and 10 Hz in a yaw rate signal are most interesting. Thus, the present invention greatly reduces the number of computations needed to obtain a frequency spectrum as compared to prior art systems and methods that conduct the Fast Fourier Transform (FFT) to obtain all possible frequencies present in the vehicle motion signal. In real time, the vehicle motion signal is multiplied by a corresponding vector in the weight filter matrix to transfer the signal from the time domain to the frequency domain.
Further objects, features and advantages of the invention will become apparent from consideration of the following description and the appended claims when taken in connection with the accompanying drawings.